MDEV-20612: Partition lock_sys.latch

We replace the old lock_sys.mutex (which was renamed to lock_sys.latch)
with a combination of a global lock_sys.latch and table or page hash lock
mutexes.

The global lock_sys.latch can be acquired in exclusive mode, or
it can be acquired in shared mode and another mutex will be acquired
to protect the locks for a particular page or a table.

This is inspired by
mysql/mysql-server@1d259b87a63defa814e19a7534380cb43ee23c48
but the optimization of lock_release() will be done in the next commit.
Also, we will interleave mutexes with the hash table elements, similar
to how buf_pool.page_hash was optimized
in commit 5155a300fab85e97217c75e3ba3c3ce78082dd8a (MDEV-22871).

dict_table_t::autoinc_trx: Use Atomic_relaxed.

dict_table_t::autoinc_mutex: Use srw_mutex in order to reduce the
memory footprint. On 64-bit Linux or OpenBSD, both this and the new
dict_table_t::lock_mutex should be 32 bits and be stored in the same
64-bit word. On Microsoft Windows, the underlying SRWLOCK is 32 or 64
bits, and on other systems, sizeof(pthread_mutex_t) can be much larger.

ib_lock_t::trx_locks, trx_lock_t::trx_locks: Document the new rules.
Writers must assert lock_sys.is_writer() || trx->mutex_is_owner().

LockGuard: A RAII wrapper for acquiring a page hash table lock.

LockGGuard: Like LockGuard, but when Galera Write-Set Replication
is enabled, we must acquire all shards, for updating arbitrary trx_locks.

LockMultiGuard: A RAII wrapper for acquiring two page hash table locks.

lock_rec_create_wsrep(), lock_table_create_wsrep(): Special
Galera conflict resolution in non-inlined functions in order
to keep the common code paths shorter.

lock_sys_t::prdt_page_free_from_discard(): Refactored from
lock_prdt_page_free_from_discard() and
lock_rec_free_all_from_discard_page().

trx_t::commit_tables(): Replaces trx_update_mod_tables_timestamp().

lock_release(): Let trx_t::commit_tables() invalidate the query cache
for those tables that were actually modified by the transaction.
Merge lock_check_dict_lock() to lock_release().

We must never release lock_sys.latch while holding any
lock_sys_t::hash_latch. Failure to do that could lead to
memory corruption if the buffer pool is resized between
the time lock_sys.latch is released and the hash_latch is released.

1 files changed, 2 insertions, 6 deletions

diff --git a/storage/innobase/row/row0merge.cc b/storage/innobase/row/row0merge.cc
index e93f64ecf1d..9b54057ac07 100644
--- a/storage/innobase/row/row0merge.cc
+++ b/storage/innobase/row/row0merge.cc
@@ -2838,12 +2838,8 @@ wait_again:
 	}
 
 	if (vers_update_trt) {
-		trx_mod_table_time_t& time =
-			trx->mod_tables
-				.insert(trx_mod_tables_t::value_type(
-					const_cast<dict_table_t*>(new_table), 0))
-				.first->second;
-		time.set_versioned(0);
+		trx->mod_tables.emplace(new_table, 0)
+			.first->second.set_versioned(0);
 	}
 
 	trx->op_info = "";